Multi function polling technique

ABSTRACT

Input devices or output devices connected to a common bus of a communications terminal are polled in response to a polling sequence specially coded to request information from either a single input device or number of input devices or status information from either input or output devices. The sequence is transmitted over a communications channel to control apparatus coupled to the bus. The control apparatus stores representations in accordance with the coding of address information items included within the sequence and initiates operations in response to and in correspondence with the stored representations.

United States Patent Heuttner et al. [4 1 Apr. 3, 1973 [541 MULTIFUNCTION POLLING 3,283,308 ll/l966 Klein ..340 172.s TECHNIQUE 3,303,4762/1967 Moyer ..340 172.5 3,407,387 Iii/i968 Looschen ..340/l72.5 Xlnvemofsl 30in" Acton; Edward 3,4l3,6l2 llll968 Brooks ..340 172.5

B. Tymann, Natick; Richard Nolin, North Andover, all of Mass. PrimaryExaminer-Paul 1. Henon Assistant Examiner-Sydney R. Chirlin [73]Assignee: Honeywell Information Systems Inc., Attorney-Ronald T. Reilinget al.

Waltham, Mass. 22 Filed: Feb. 11, 1971 [57] ABSTRACT [21] Appl Na: 4,431Input devlces or output devlces connected to a common bus of acommunications termmal are polled 1n response to a polling sequencespecially coded to [52] U.S. Ci. ..340/172.5 request information fromeither a single input device [5 1] Int. Cl. ..G06i 9/18 or number ofinput devices or status information from [58] Field of Search..340/l72.5 either input or output devices. The sequence is transmittedover a communications channel to control ap- [56] References Citedparatus coupled to the bus. The control apparatus stores representationsin accordance with the coding UNITED STATES PATENTS of addressinformation items included within the 3,573,741 4 1971 Gavril..340/172.s Sequence and initiates Operations in response to and in3,559,l84 l/l97l Rawlings.. ...340/l72.5 correspondence with the storedrepresentations. 3,539,998 i/l970 Belcher.... ...340Ii72.5 3,210,733l0/l965 Terzian ..340/l72.5 41 Claims, 31 Drawing Figures OOIlTROl. lOZ

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PATENT 3,725.87 1

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PATENIFDIPIICS I973 3,725,871

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1. A method of polling a plurality of data handling devices of a remotestation to process a plurality of different types of requests, saidmethod comprising the steps of: transmitting to said station firstinformation item signals denoting an address identification of saidstation, and a designation as to whether said station is to transferdata or supply status information; transmitting to said station secondinformation item signal denoting an address identification of at leastone of said devices, and a designation of whether said device is totransmit or receive data; receiving said second information item signalsat said station, in response to the address identification denoted bysaid first information item signals; storing representations of saiddesignation of said received information item signals of said station;and effecting an operation in said device at said station in response toand in correspondence with said stored representations.
 2. The method ofclaim 1 further including the step of sensing control signals generatedby said data handling device identified when said device is to supplystatus information and transmitting from said station a messageindicating that said device is ready to transfer data, is busy andunable to transfer data, or is inoperative.
 3. The method of claim 1wherein said information item signals identifying said device are codedwith a predetermined bit configuration for specifying that a pluralityof said devices are to supply data.
 4. The method of claim 3 whereinsaid predetermined bit configuration corresponds to a ZERO code.
 5. Themethod of claim 1 wherein said first information item signals define asystem addreSs character, As, including a status/data bit, S, and aplurality of station identification bits, At, and said secondinformation items signals define a device address character, Ad,including an input/output bit, I/O, and a plurality of deviceidentification bits, Ad, said As and Ad characters being coded asfollows for requesting data from a single addressed data handlingdevice, all input devices, and status information from a single input oroutput device respectively:
 1. At terminal station address, S 0; Ad not= 0, and I/O 1;
 2. At terminal station address, S 0, Ad 0 and I/O ; and3. At terminal station address, S 1, Ad not = 0 and I/O 1 or
 0. 6. Themethod of claim 5 wherein said As and Ad characters are coded as followsfor requesting data be received by a single addressed data handlingdevice: At terminal station address, S 0, Ad not = 0, and I/O
 0. 7. Themethod of claim 5 wherein said Ad character includes at least oneadditional bit which is coded as the complement of said input/outputbit.
 8. The method of claim 5 wherein said As and Ad characters comprisea multicharacter multifunction polling sequence which further includesan end of transmission control character as a first character forinitiating said station to a predetermined state and an enquiry controlcharacter as a last character.
 9. The method of claim 1 furtherincluding the steps of : sensing the presence of a predetermined code;and, generating a first control signal for inhibiting the transmissionof further data characters to a data processing system by said stationin response to sensing said predetermined code until said stationreceives information signals from said data processing systemacknowledging said transmission as good.
 10. The method of claim 9further including the steps of: sensing the number of data characterstransmitted to said data processing system; and, generating a secondcontrol signal for inhibiting the transmission of further datacharacters when a predetermined number of said characters have beentransmitted without said sensing of said first control signal until saidstation receives said acknowledgement signals.
 11. The method accordingto claim 10 further including the steps of: transmitting informationsignals denoting address identification of said station and said devicefor each first group of data characters transferred by a device and eachgroup of data characters in which said first control signal is sensed;and, inhibiting the transmission of said address identification signalswhen said second control signal is sensed.
 12. The method according toclaim 11 wherein said method further includes the steps of: transmittingan end of text character signals at the end of said data characters inresponse to said first control signal; and, transmitting an end of blockcharacter signals at the end of each group of data characters inresponse to each of said second control signals.
 13. A method of pollinga plurality of peripheral devices of a communications terminal by aremote data processing system to condition a communications controlapparatus coupled to said terminal to process a plurality of differenttypes of requests, said method comprising the steps of: generating aplurality of signals representing an initial message sequence coded toinclude a first address character for identifying said terminal and forspecifying whether said terminal is to transfer data or supply statusinformation, and a second address character coded to specify one or moreof said devices, and whether each said device is to transmit or receivedata; transmitting said message sequence to said terminal communicatioNscontrol apparatus; receiving said message sequence in response to saidfirst address character according to said message sequence by saidcontrol apparatus; storing the results of said decoding by switchingpredetermined ones of a plurality of state bistable devices inaccordance with said coding; combining the outputs of said bistabledevices so as to define a plurality of procedures for processing saiddifferent requests; and, selecting a predetermined one of saidprocedures in accordance with the coding of said address informationcharacters.
 14. The method of claim 13 wherein said predetermined bitpositions of said second address are coded to an unassignedpredetermined code for specifying a plurality of devices.
 15. The methodof claim 14 wherein said predetermined device code is a ZERO code. 16.The method of claim 13 wherein predetermined bit positions within saidmessage sequence are coded so as to be complementary of one another toprotect against erroneous decoding of said message characters.
 17. Themethod of claim 13 further including the steps of: sensing controlsignals generated by said device interrogated for status; and,transmitting to said remote data processing system one of a plurality ofmessages indicating that said device is ready to transfer data, is busy,or is inoperative.
 18. The method of claim 17 wherein said plurality ofmessages for said responses include the following respective charactersequences; DLE, phi , DLE,A, and DLE,B.
 19. The method of claim 13wherein said first address character includes a status/data bit, S, anda plurality of terminal identification bits, At, and said second addresscharacter includes an input/output bit, I/O, and a plurality ofidentification bits, Ad, said first and second characters being coded asfollows for specifying a device poll, a system poll and status pollrespectively:
 1. At terminal address, S 0, Ad device address and I/O, 1;2. At terminal address, S 0, Ad 0 and I/O 1; and,
 3. At terminaladdress, S 1, Ad device address and I/O 1 or 0 for specifying either aninput device or output device respectively.
 20. The method of claim 13wherein said first and second address characters are coded as followsfor specifying a device selection request: At terminal address, S 0, Addevice address and I/O
 0. 21. The method of claim 13 wherein said secondaddress character includes at least one additional bit which is coded asthe complement of said input/output bit.
 22. The method of claim 13wherein said first and second characters comprise a multicharactermultifunction polling sequence which further includes an end oftransmission control character as a first character of said sequence forinitializing said terminal to a predetermined state and an enquirycontrol character as a last character of said sequence.
 23. The methodof claim 22 wherein each of said characters of said polling sequence iscoded in ASCII code.
 24. The method of claim 13 further including thesteps of : sensing the presence of a predetermined code within said datacharacters being transmitted; and generating a first control signal forinhibiting the transmission of further data characters from said deviceto said data processing by said communications control apparatus inresponse to said predetermined code until said control apparatusreceives information signals acknowledging said transmission as good.25. The method of claim 24 further including the steps of: sensing bysaid communications control apparatus the number of data characterstransmitted to said data processing system; and, generating a secondcontrol signal for inhibiting the transmission of further datacharacters when a predetermined number of said characters have beentransmitted in the absence of said first control signal until saidcommunications apparatus receives said acknowledgement signals.
 26. Themethod of claim 25 further including the steps of: transmittinginformation signals denoting address identification of said terminal andsaid device by said communications apparatus for each first block ofdata characters transferred to said apparatus by said device and foreach block of said data characters in which said first control signal issensed; and, inhibiting the transmission of said address identificationsignals by said communications control means when said second signal issensed.
 27. The method of claim 26 wherein said address identificationsignals are transmitted as part of the sequence: SOH, As and Ad.
 28. Themethod according to claim 26 wherein said method further includes thesteps of: transmitting an end of text character signals at the end ofeach block in response to said first control signal; and, transmittingan end of block signal within a series of blocks in response to each ofsaid second control signals.
 29. In a remote terminal system including adevice scanner control means, a plurality of peripheral devicesinterconnected through one of a number of device control means to saidscanner control means through a common bus, a communications controlmeans for processing different types of polling requests transmittedover a communications channel from a control station defined by aninitial message sequence including address characters identifying saidterminal system and at least one device, said communications controlmeans being coupled to said channel and said bus, said control meanscomprising: decoding means connected to receive and decode each of thecharacters of said initial sequence in response to said terminal addresscharacter, said decoding means including a plurality of bistable storagemeans for storing indications of the results of decoding and informationpertinent to the processing of a specified one of said different typesof polling requests transmitted by said control station; and, receivesubcommand generating means coupled to said decoding means forgenerating control signals to said bus for selectively conditioning saidscanner control means and said devices control means for processing saiddifferent types of polling requests.
 30. The system of claim 29 whereinthe state of a first one of said bistable storage means defines a pollrequest; the state of a second one of said bistable storage meansdefines a status poll request; the state of a third one of said bistablestorage means defines a multiple poll request; and, said communicationscontrol means further including a plurality of additional bistablestorage means connected to store digital indications of said deviceaddress codes in response to predetermined types of said pollingrequests.
 31. The system of claim 30 wherein said first bistable meansis switched to a ONE only when a predetermined bit of one of saidaddress characters is set to a predetermined state and said secondbistable means is switched to a ONE only when said predetermined bit isset to a state complementary to said predetermined state.
 32. The systemof claim 30 wherein said third bistable means is switched to its ONEstate only when predetermined bit positions of another one of saidaddress characters are set to predetermined states.
 33. The system ofclaim 30 further including a fourth bistable means, said fourth bistablemeans being switched to a ONE state for defining a selection requestonly when a predetermined bit position of said second address characteris set to a state complementary to the state of said bits for definingsaid poll requests.
 34. The system of claim 32 wherein saidpredetermined states are all ZEROS.
 35. A remote system connected toprocess different types of polling Requests in the form of an initialmessage sequence from a central station over a communications channel,said sequence including address characters coded to identify saidterminal system and at least one device, said remote terminal systemcomprising: a bus including a plurality of data and control lines; aplurality of peripheral devices; a plurality of device control means forinterconnecting at least one of said devices to communicate with saidbus; a device scanner, said device scanner including address generatingmeans for generating address codes of said plurality of input devicesand decoding means coupled to said generating means connected to detecta predetermined character code and condition said address generatingmeans to increment to the address code of a next input device; acommunications control means coupled to said bus and to saidcommunications channel, said communications control means including,decoding means coupled to said communications line and operative todecode each of the address characters of said initial sequence, saiddecoding means including storage means conditioned to store the resultsof said decoding and information pertinent to the processing of one ofsaid different types of polling requests, subcommand generating meanscoupled to said decoding means and being conditioned to generate controlsignals for processing each of said requests, and bus logic meanscoupled to said subcommand generating means and to said bus, said buslogic means being conditioned by said generating means to selectivelyenable said scanner decoding means to condition said address generatingmeans to poll each of the input peripheral devices for data inaccordance with a predetermined state of said storage means.
 36. In thesystem of claim 35 wherein predetermined ones of said storage means arein predetermined states to indicate a system poll request.
 37. In thesystem of claim 35 wherein said scanner and device control means eachinclude logic means for switching same to an active state for processingsaid requests, said communication means being operative in accordancewith said state of said storage means to condition said bus logic meansto apply a predetermined signal to said bus for inhibiting each of saidlogic means from switching said scanning means and said device controlmeans to an active state when conditioned to process a status request.38. The system of claim 37 wherein said bus logic means includes meanscoupled to said bus for sampling predetermined ones of said bus linesfor determining the state of said device polled.
 39. In the system ofclaim 35 wherein said communications means further includes: memorymeans coupled to said bus and to said communications line, memory means,said memory means being conditioned by said subcommand generating meansduring processing of a first type of request to transfer data charactersto said communications line from each input device in sequence inresponse to a complete cycling of said scanner address generating meanswhereafter said communications means terminates processing of saidrequest.
 40. In the system of claim 39 wherein said memory means furtherincludes: a first addressable storage means including a predeterminednumber of character locations; a second addressable storage meansincluding a predetermined number of character storage locations; and,memory switching means coupled to said first and second storage means,said memory switching means being operative to transfer data charactersfrom an input device to a predetermined one of said storage means, andsaid memory switching means including logic means coupled to said memorymeans and to said bus, for sensing when the one of said storage meansinto which data characters are being written is full and when the otherone of said storage means is available, said sensing means beingoperative to condition said memory switching means to switch storagemeans for writing data characters into said other storage means wherebysaid transfers between said bus and said memory storage means and saidcommunications line and said storage means proceed simultaneously. 41.In the system of claim 40 wherein said communications means furtherincludes state control means coupled to said decoding means; and,message generation means coupled to said decoding means and to saidmemory switching means, said message generation means being conditionedby said memory switching logic means and state control means to generateinformation identifying the source of blocks of data characters for eachof the first blocks of each block of data characters transferred by eachinput device for transmission to said central station.